Badania modeli aeroelastycznych przewodów linii wysokiego napięcia dla różnych przypadków ich ośnieżenia i oblodzenia

In the first part of this paper, similarity criteria were elaborated for investiga-tions of aeroelastic sectional models of high voltage line wires. These criteria consider wire vibrations caused by aeroelastic phenomena: vortex excitation, wake galloping and interfer-ence between the wires causing vibration in aerodynamic trace of other wires. Second part of the paper describes the tests conducted in Wind Engineering Laboratory of Cracow Univer-sity of Technology. The subject of this set of tests was identifi cation of aeroelastic vibrations caused by aeroelastic interference of wires, mainly determination of critical velocity of wires galloping and wake galloping for selected cases of snow and ice covers on the wires.W pierwszej części pracy wyprowadzono kryteria podobieństwa dla badańmodeli aeroelastycznych odwzorowujących przewody linii wysokiego napięcia. Kryteria te uwzględniają drgania przewodów przy występowaniu zjawisk aeroelastycznych: wzbudzenia wirowego, galopowania oraz interferencji i drgania w śladzie aerodynamicznym innych prze-wodów. Druga część pracy przedstawia przeprowadzone w Laboratorium Inżynierii Wiatrowej Politechniki Krakowskiej badania modeli aeroelastycznych wiązki trzech przewodów linii wy-sokiego napięcia. Badania te miały na celu identyfi kację drgań aeroelastycznych spowodowa-nych wzajemną interferencją przewodów, a w szczególności wyznaczenie prędkości krytycznej dla galopowania przewodów dla wybranych przypadków ośnieżenia i oblodzenia przewodów

Influence of the wind tunnel model characteristics on the loading and response of cable-net hyperbolic paraboloid roofs

Aerodynamic modelling affects the prediction of wind loads if they are derived from wind tunnel tests. Depending on the structural type, difference in applied loads may induce larger or smaller differences in the predicted structural response. For low rise buildings, the roof roughness is a crucial parameter that affects the wind action distribution and magnitude, and its impact on the structural response. This paper discusses the results from wind tunnel pressure measurements on eight geometries of hyperbolic paraboloid roofs, coming from experimental campaigns in three different wind tunnels and using different models. The pressure distributions are then used to evaluate vertical displacements of cable nets tensile structures, which are also compared with each other. Results show that significant differences in the measured pressures are only slightly reduced when vertical displacements are compared, that is inaccuracy of the load is only slightly mitigated when propagated to the response

Dynamics of a Flexible Roof Test Model under Ambient Vibrations Measurements

Flexible roofs are sensitive to wind actions because they are light, and their deformability can induce local or global instability. In most cases, their design requires experimental wind tunnel testing to investigate the aeroelastic phenomena and the structural response under the wind. However, the reduced scale necessary in wind tunnels makes the dynamic identification of the test model difficult. Several approaches of multi-modal dynamic identification can be used, even if a specific approach is not defined for geometric nonlinear flexible roofs. Many times, the choice of the position of the sensors is affected by the unknown roof dynamics. This paper investigates the ambient vibration time-dependent accelerations for a flexible roof scaled model through Singular Value Decomposition (SVD) and their spatial correlations with the purpose of analyzing the signal structure and its acquisition to perform the dynamic identification of the test model